Glass fiber reinforced polycarbonate resins can have excellent mechanical strength, heat resistant and the like, and accordingly have been used for electric/electronic parts and other applications requiring high heat resistance and dimensional stability.
Conventionally, halogen based flame retardants, phosphoric compounds, or antimony compounds have been used to impart flame retardancy to polycarbonate resins. However, the use of halogen based flame retardants has been strictly limited because of gases generated during combustion, which are harmful to the human body. Phosphoric acid ester based flame retardants, which are examples of phosphoric compound flame retardants, can deteriorate heat resistance and mechanical strength, and thus the use of phosphoric acid ester based flame retardants has been limited.
Metal salt based flame retardants do not include a halogen compound and further can impart high heat resistance and flame retardancy. However, it can be difficult to impart a flame retardancy rating of V0 (measured in accordance with the UL 94 flameproof test using a 1.5 mm thick specimen) to a glass fiber reinforced polycarbonate resin using only the metal salt based flame retardant because of the glass fiber itself.
In this regard, the flame retardancy of glass fiber reinforced polycarbonate resin is significantly deteriorated due to the high thermal conductivity of the glass fiber. Accordingly, the glass fiber can conduct heat into the resin and in this manner can deteriorate the flame retardancy of the resin.
To solve this problem, an organic silicone based compound can be used along with the flame retardant. The silicone based compound, however, should be used in an amount of 2.0% by weight or more to achieve a V0 flame retardancy rating. However, adding 2.0 parts by weight or more of the organic silicone based compound to the resin can deteriorate flexural strength, flexural modulus and thermal resistance, and, in the case of a liquid phase silicone based oil, productivity.
Japanese Patent Publication No. 1972-40445 is directed to a method of improving the flameproof properties of an aromatic polycarbonate without using a brominated flame retardant. The method includes mixing aromatic polycarbonate with an alkali metal salt or alkaline earth metal salt of perfluoroalkane sulfonic acid. Japanese Patent Publication No. 1985-38418 is directed to a method of mixing aromatic polycarbonate with organic alkali metallic salt or alkaline earth metallic salt and polytetrafluoroethylene to prevent dripping during combustion. However, these aromatic polycarbonate resin compositions do not include glass fiber.
US Patent Application Publication No. 2007/0191518 is directed to a flameproof resin composition comprising polycarbonate, glass fiber, polysiloxane-polycarbonate copolymer, aromatic sulfone sulfonate, such as potassium diphenylsulfone sulfonate, and aromatic sulfonate such as sodium salt of toluene sulfonic acid. The examples in this application include only 9 parts by weight of the glass fiber, and it is well known in the art that the flame retardancy of a polycarbonate resin including glass fiber significantly deteriorates with increasing amounts of glass fiber. Also, the publication requires a polysiloxane-polycarbonate copolymer and aromatic sulfonate to increase flame retardancy.
Korean Application Publication No. 10-2005-0120238 is directed to a flameproof resin composition comprising polycarbonate, glass fiber, a metal salt of perfluoroalkane sulfonic acid and a polyorganosilsesquioxane based silicone compound. However, the composition requires the polyorganosilsesquioxane based silicone compound and further includes only 2 to 8 parts by weight of the glass fiber to achieve a V0 rating measured in accordance with the UL94 flame retardancy test.
Korean Application Publication No. 10-2008-0062503 is directed to a composition comprising polycarbonate resin, fluorinated polyolefin based resin, a metal salt of perfluoroalkane sulfonic acid, and an organic siloxane polymer. However, this composition does not include glass fiber. Moreover, this composition includes only one kind of polymethylphenylsiloxane in an amount of 2 to 3 parts by weight.